[Nook Color General] a.fenderson:
[ANECDOTE]

micksh mentioned earlier in the thread that Windows Phone 7 certified microSD cards are very recently starting to appear, and the only info I could find on it led me to believe that availability is limited, mainly to AT&T physical stores (in fact an AT&T online chat rep directed me to a B&M store). So, today I paid my local AT&T mobile store a visit.

I walked in, was asked what I might need help with, and, well, here are excerpted approximations of what then was said:

me: "I'm looking for Windows 7 Phone certified microSD cards, do you have any?"

him: (instantly) "There's no such thing."

...

him: "I've never heard of Windows 7 certified SIM cards."

me: "Well, I'm actually looking for microSD cards."

him: "Yeah, that's what I meant."

...

him: "I really don't think Windows certifies SIM cards."

me: "OK, but I'm looking for microSD cards."

him: "I'm sorry, that's what I meant."

...

(after spending an entire 5 seconds doing a Google search):

him: "There's no such thing as Windows certified SD cards, but there are certain ones that do work, like Scan (sic) Disk Class 4."

(I didn't feel like further correcting him)

...

him: "You might try Wal Mart, see if you can find some of those Scan (sic) Disk cards, I can write it down for you."

Well, at least he was trying to help--somewhat. But the thing is--the guy sees SanDisk cards every day: they carried two different kinds in the store, and he admitted they had stocked those cards the entire time he had worked there. Good times. :-)

[/ANECDOTE]

Better sequential reads are possibly helpful or even necessary for relatively high bitrate videos, if you're playing around with bitrates over 1MB/s (8000 kb/s), which I've done a bit with M-JPEG (up around 18 Mbit/s or 2.25 MByte/s) and am experimenting with for hardware-decoded H264. I've also assumed that even the small-block random read speeds might affect playback of files with bitrates this high, if your files aren't perfectly unfragmented on the card. But it seems like most everyone who's just trying to get basic hardware-decoded H264 to work is using somewhere in the neighborhood of 1000 Kb/s to 3000 Kb/s (0.125 MB/s to 0.375 MB/s), and from the testing I've done, most cards seem to have a minimum of right around 1 MB/s random read and generally much higher sequential read.

Speaking of card testing, here's my latest:

4GB SanDisk Class 2 microSDHC card

card history: multiple rewrites

card origin: came with Samsung Acclaim phone

Sequential Read : 4.204 MB/s
Sequential Write : 2.648 MB/s
Random Read 512KB : 4.215 MB/s
Random Write 512KB : 1.249 MB/s
Random Read 4KB (QD=1) : 1.896 MB/s [ 462.9 IOPS]
Random Write 4KB (QD=1) : 1.074 MB/s [ 262.3 IOPS]
Random Read 4KB (QD=32) : 1.850 MB/s [ 451.6 IOPS]
Random Write 4KB (QD=32) : 0.891 MB/s [ 217.4 IOPS]

Here's the latest compilation, now with NOTEs(TM)!, but still sorted on small-block random write speed only. If anyone has posted / does post results using a reader/pc/etc other than the setup they originally used, and/or posts multiple benchmarks for the same physical card, please make a note of that in your post (as chinly43 and Awats did) so I can at least carry the note over into the spreadsheet.

micro SD card 4KB random write (QD32) benchmarks posted thus far in this thread:

POSTER	BRAND	CLASS	CAPACITY (GB)	4 KB RANDOM WRITE QD32 (MB/s)	NOTE
swoozle	SanDisk	2	8	1.791
a.fenderson	SanDisk	4	16	1.660	SanDisk C4 16GB 1 of 2 cards
a.fenderson	SanDisk	4	16	1.500	SanDisk C4 16GB 2 of 2 cards
Awats	SanDisk	4	16	1.391	SanDisk C4 16GB 1 of 2 cards ; fastest (onboard) reader
Awats	SanDisk	4	16	1.284	SanDisk C4 16GB 2 of 2 cards ; fastest (onboard) reader
robot8	SanDisk	4	8	1.259
chinly43	SanDisk	4	16	1.257	(not via Nook) ; same card as chinly43's other listed SanDisk C4 16GB
joobu	SanDisk	4	4	1.175
angomy	Nook internal	N/A	N/A	1.116	via Nook on USB
chinly43	Nook internal	N/A	N/A	1.094	via Nook on USB
a.fenderson	Transcend	2	32	1.032
a.fenderson	SanDisk	4	4	0.898
a.fenderson	SanDisk	2	4	0.891
chinly43	SanDisk	4	16	0.769	via Nook on USB ; same card as chinly43's other listed SanDisk C4 16GB
chinly43	SanDisk	2	8	0.616
a.fenderson	SanDisk	4	8	0.596
angomy	SanDisk	4	16	0.574
a.fenderson	SanDisk	N/A	2	0.269
Awats	SanDisk	4	2	0.261	SanDisk C4 2GB 1 of 2 cards ; fastest (onboard) reader
Awats	SanDisk	4	2	0.236	SanDisk C4 2GB 2 of 2 cards ; fastest (onboard) reader
joobu	Lexar	4	8	0.038
swoozle	Patriot	10	8	0.038
chinly43	SanDisk	N/A	1	0.029
joobu	??	N/A	2	0.029
swoozle	Transcend	6	8	0.029
a.fenderson	SanDisk	N/A	1	0.028
ExploreMN	Patriot	10	16	0.018
robot8	Transcend	6	8	0.018
Awats	Patriot	4	4	0.016	Patriot C4 4GB 1 of 2 cards ; fastest (onboard) reader
swoozle	Kingston	4	4	0.016
a.fenderson	Kingston	4	8	0.014
Tnexus	Patriot	10	16	0.014
Awats	Patriot	4	4	0.011	Patriot C4 4GB 2 of 2 cards ; fastest (onboard) reader
chinly43	Lexar	4	8	0.011